Method and apparatus for completely or partly covering at least one electronic component with a compound

ABSTRACT

A method and apparatus for at least partly covering at least one electronic component with compound, the apparatus being provided with a first mold half and a second mold half, the first mold half being moveable relative to the second mold half, while means are provided for placing an electronic component on a mold half for inclusion of this component in a mold cavity defined by the two mold halves, the first mold half being provided with a number of actuators with the aid of which the position of the first mold half relative to the second mold half is continuously and accurately regulable, while the distance between the two mold halves is continuously regulated and, if desired, adjusted during the two mold halves being moved towards each other and during their being held in a position when moved towards each other.

The invention relates to a method according to the preamble of claim 1.

The invention also relates to an apparatus according to the preamble ofclaim 11.

Such a method and apparatus are known from U.S. Pat. No. 6,346,433 andEP-A-0 971401.

The drawbacks of the known method and apparatus are inter alia that inthem, the mold halves in the position when moved towards each other arepressed together with force. Accordingly, in technical jargon, the termpressing is used. The distance between the mold halves is determined bythe mutual contacting surfaces of the mold halves, i.e. the surfaceswhich, with the mold in closed condition, are pushed against each other.Under the influence of various circumstances, varying from preparationtolerances, material stresses in the mold, tolerances on the carrier ofthe product to be encapsulated, and external circumstances such as, forinstance, temperature and the like, it may occur that the mold halvesare not or cannot be properly pressed together. Then, the encapsulatingmaterial will fill up this space at those locations where there is roomto that end, and bleed and flash occur. Another consequence is that themold cavity dimensions can deviate. In particular with electroniccomponents provided with a chip with sensor function or contact surfaces(so-called solder bumps or upwardly or downwardly protruding contactpoints) such a deviating mold cavity dimension can result in the sensoror the bumps being covered with compound, which renders the electroniccomponent unusable.

The invention contemplates a method and an apparatus with which theseproblems are remedied.

To this end, the method and apparatus described in the opening paragraphare characterized by the features of claims 1 and 11, respectively.

The position controlled regulation of the mold halves relative to eachother makes it possible to adjust away deviations occurring due toexternal factors. The necessity of pressing the mold halves togetherwith great force is thereby eliminated. As a result, an apparatusaccording to the invention can be constructed to be much lighter thanthe known presses for covering electronic components with compound.Generally, a lighter construction allows for the mold halves to be movedmore rapidly relative to each other, thereby obtaining a greatercapacity. Moreover, as a rule, lighter constructions are advantageousfrom a point of view of costs. Another advantage is that due to theposition controlled actuators and the associated control, an operationis obtained with which the rate of the mold having moving towards eachother can be accurately regulated; thus, for instance, the flow patternand the flow rate of the compound over the electronic compound can beinfluenced.

Furthermore, by working with several actuators, the plan parallelism ofthe two mold halves relative to each other can each time be adjusted ifnecessary. Moreover, with the method and apparatus according to theinvention, it can be ensured that with the mold halves in the positionwhen moved towards each other, for instance bumps or such upwardly ordownwardly protruding contact points of the electronic component abutagainst one of the mold halves and therefore remain clear of compoundwhen the compound cures. The mold halves can be covered or not becovered with film to simplify keeping the contact surfaces clear andkeeping the mold half (halves) clear from compound. The film sidecontacting the contacts points can be provided or not be provided withan adhesive layer.

By accurately positioning the mold halves relative to each other, theimpression of the film can be very well controlled and forces on thechip or carrier are minimal. In this manner, it can be ensured that theelectronic component need not undergo a finishing operation for removingcompound from the contact points or bumps. The functional area of asensor chip will remain bleed- and flash-free.

Optionally, in addition to the position control of the mold halves,force feedback control can take place. The apparatus can for instance“feel” whether the moveable mold half has already contacted theelectronic component. However, it is self-evident that also differentmethods and elements can be used to ensure a desired distance betweenthe mold halves. For instance, sensors for determining the distancebetween the mold halves can be provided on the mold halves, optionallyat different positions. The signals of these sensors can then be usedfor adjusting the mutual position of the mold halves relative to eachother.

According to a further elaboration of the invention, the method and theapparatus are characterized by the features of claims 2 and 12,respectively.

As the mold halves are held at a small distance from each other, acertain position control range is maintained. It is self-evident thatmeasures have to be taken to prevent compound from undesirably flowingaway between the mold halves. This can for instance be effected byallowing the distance between the mold halves to be very small, forinstance in the order of some micrometers. On the other hand, it is alsopossible that one of the mold halves is provided with a resilientlyarranged ring surrounding the mold cavity. Such resilient rings are alsoknown from molds for manufacturing CD's and DVD's and are indicated inthat field of technology with the term venting ring. Such a resilientlyarranged venting ring is connected to the one mold half and, with themold halves in the position when moved towards each other, contacts theother mold half. As the ring is arranged to be resilient, this ring doesnot further influence the relative distance between the mold halves.This relative distance—and hence the dimensions of the mold cavity—isdetermined by the control which controls the actuators in a desiredmanner. The actuators can comprise, for instance, screw spindles drivenby servomotors. Linear servomotors are a possibility too. It is ofimportance that with the actuators, a continuous position control rangeis obtained. With modern high performance servocontrols, optionallysupplemented with a force feedback control superposed thereon, anexceptionally accurate and flexible apparatus can be obtained.

When encapsulating semiconductor products, it is of importance thatduring filling, the filled material is brought to a high pressure. Inelectromechanical presses used nowadays, the closing force is appliedalready from the moment of closing up.

By measuring the viscosity of the compound and the pressure in thecompound, the force of compression of the compound can be regulated.

Further elaborations of the invention are described in the subclaims andwill be further elucidated hereinafter with reference to the drawing.

FIG. 1 shows a schematic cross sectional view of a first exemplaryembodiment of an apparatus according to the invention with mold halvesmoved apart;

FIG. 2 shows a cross-sectional view of the exemplary embodimentrepresented in FIG. 1 with mold halves moved towards each other;

FIG. 3 shows a cross-sectional view of a second exemplary embodimentwith mold halves moved apart;

FIGS. 4-6 show the various stages of two mold halves being moved towardseach other; and

FIG. 7 shows a side view of the application of a compound on anelectronic component.

All Figures show a first mold half 1 and a movably arranged second moldhalf 2. In the exemplary embodiment shown, the position of the secondmold half is regulated by four actuators 3 connected to the cornerpoints of the second mold half 2. The actuators 3 can for instancecomprise servomotors 3 a, each driving a screw spindle 3 b via a screwspindle nut 3 c. Upon rotation of the screw spindle nut 3 c, theassociated screw spindle 3 b undergoes an axial displacement. The secondmold half 2 is provided with bearings 3 d in which the extremities ofthe screw spindles 3 b are bearing mounted.

In the present exemplary embodiment, the mold halves 1, 2 are eachprovided with a recess 4, 5 together defining a mold cavity when themold halves 1, 2 are in the position when moved towards each other. Inthe recess 4 of the first mold half 1, an electronic component E isplaced. The electronic component E can comprise, for instance, a waferwith a number of chips formed thereon. However, with the method andapparatus according to the invention, other electronic components toocan at least partly be covered with a compound. In the present case, theelectronic component is provided with bumps or upwardly protrudingcontact points B.

In FIG. 1, an amount of compound C has been placed on top of theelectronic component E. By moving the mold halves 1, 2 towards eachother, the compound is compressed and it flows over the electroniccomponent E, thereby completely filling the mold cavity 4, 5 withcompound C. The position in which the mold halves have been movedtowards each other is shown in FIG. 2. It is clearly visible that thescrew spindles 3 b have been taken up further into the actuator housing3. It is also clearly visible that the mold halves 1, 2 are not pressedonto each other but that between them, a certain distance is maintained,so that the relative positions of the mold halves 1, 2 can becontinuously adjusted by the actuators 3. Adjustment can take place onthe basis of, for instance, signals provided by sensors. Accurateproximity sensors 6 could serve to this end. Optionally, in the screwspindles 3 b or the actuator housings 3, force detectors can be includedwith which axial forces are detected. Via a force feedback controlsuperposed on the position control, the position controlled actuatorscould further adjust the relative position of the mold halves 1, 2. Itis self-evident that for all this, a control 7 is required, connected tothe actuators 3 and the optional sensors 6. The compound can, forinstance, be a thermoset which is cured at a mold temperature of 80-180°C., depending on the sort of compound used.

The second exemplary embodiment represented in FIG. 3 shows a similarapparatus wherein a film supply and discharge device 8 for the firstmold half 1 and a film supply and discharge device 9 for the second moldhalf 2 are shown. The film F1, F2 can, for instance, be a release filmeffecting the easy release of the compound C from the mold cavities 4,5. Moreover, the lower film F1 can also be used for supply and dischargeof the electronic component E.

FIGS. 4-6 show the different phases of the mold halves moving towardseach other. From FIG. 6 too, it appears once more that the mold halves1, 2 do not contact each other in the position when moved towards eachother, so that their relative position remains adjustable. In theexemplary embodiment shown this is of importance because then, it can beeffected that the inside surface of the recess 5 in the second mold half2 can be positioned accurately against the bumps B of the electroniccomponent E. This prevents contamination of the upper side of thesebumps by compound.

Finally, FIG. 7 schematically shows in what manner an electroniccomponent E can be provided with compound C with the aid of an inkjethead 10. The electronic component thus provided with compound can beplaced into the mold cavity to have the compound cure in the desiredfinal shape there.

It will be clear that in an apparatus and method according to theinvention, one of the mold parts can move, a part which may or may notcarry the component E, while also both parts may be movable.

It will be clear that the invention is not limited to the exemplaryembodiment described, but that various modifications are possible withinthe framework of the invention.

For instance, provisions can be present for automatically placing anddischarging a component into and from the mold halves, respectively.Compound supply provisions other than those shown in the Figures arepossible too. An alternative is described for instance in EP-A-0971401,the content of which is understood to be incorporated herein byreference. For that matter, the teaching of U.S. Pat. No. 6,346,433 isalso understood to be incorporated herein by reference.

1. A method for completely or partly covering at least one electroniccomponent with a compound, wherein in a suitable order, the followingsteps are traversed: a) the at least one electronic compound is placedon a mold half; b) the electronic compound is completely or partlycovered with the compound; c) a second mold half which is moveablerelative to the first mold half is moved in the direction of the firstmold half; characterized in that e) the distance between the two moldhalves is continuously regulated and, if desired, adjusted during thetwo mold halves being moved towards each other and during the two moldhalves being held in a position when moved towards each other during thecuring of the compound.
 2. A method according to claim 1, wherein, inthe position when moved towards each other, the mold halves are held ata small distance from each other, so that in the position when movedtowards each other too, a certain position control range is maintained.3. A method according to claim 1 or 2, wherein step b) takes place afterthe mold halves have been brought into the position when moved towardseach other.
 4. A method according to claim 3, wherein the compound isinjected into the mold cavity.
 5. A method according to claim 3, whereinthe compound is placed in the mold cavity and during the mold halvesbeing moved towards each other is compressed so as to be spread in themold cavity.
 6. A method according to claim 1 or 2, wherein step b)takes place before the mold halves have been brought into the positionwhen moved towards each other.
 7. A method according to claim 6, whereinthe compound is placed on the electronic component and, together withthe component, is placed on the mold half.
 8. A method according toclaim 7, wherein the placement of the compound is effected by an inkjettechnique, so that the compound is placed on the desired positions onthe electronic component.
 9. A method according to any one of thepreceding claims, wherein a film is placed between the electroniccomponent and at least one mold half.
 10. A method according to claim 9,wherein the film also serves for supplying and/or discharging theelectronic component into or from the mold cavity, respectively.
 11. Anapparatus for carrying out the method according to any one of thepreceding claims, wherein the apparatus is provided with a first moldhalf and a second mold half, wherein the first mold half is moveablerelative to the second mold half, while means are provided for placingan electronic component on a mold half for inclusion of the component ina mold cavity defined by the two mold halves, characterized in that thefirst mold half is provided with a number of actuators with the aid ofwhich the position of the first mold half relative to the second moldhalf is continuously and accurately regulable, the apparatus beingprovided with a control for regulating the positions of said number ofactuators, so that the distance between the two mold halves iscontinuously regulated, and, if desired, adjusted during the two moldhalves being moved towards each other and during the two mold halvesbeing held in a position when moved towards each other.
 12. An apparatusaccording to claim 11, wherein the control is arranged for holding thetwo mold halves at a small distance from each other in the position whenmoved towards each other, so that in the position when moved towardseach other too, a certain position control range is maintained.
 13. Anapparatus according to claim 11 or 12, wherein a component supply anddischarge device is provided, which is arranged for placing and removingan electronic component on or from said mold half, respectively.
 14. Anapparatus according to any one of claims 11-13, wherein a film supplyand discharge device is provided for supplying film to the mold cavityand discharging film from the mold cavity.
 15. An apparatus according toclaims 13 and 14, wherein the film supply and discharge device alsoforms the component supply device.
 16. An apparatus according to any oneof claims 11-15, provided with a compound supply provision.
 17. Anapparatus according to claim 16, wherein the compound supply provisionis arranged for supplying the compound to the mold cavity when the moldhalves are in the position when moved towards each other.
 18. Anapparatus according to claim 16, wherein the compound supply provisionis arranged for placing the compound on an electronic component which isplaced on a mold half.
 19. An apparatus according to claim 16, whereinthe compound supply provision is arranged for placing compound on anelectronic component present outside the mold cavity.
 20. An apparatusaccording to claim 18 or 19, wherein the compound supply provisioncomprises an inkjet head and a compound reservoir connected to theinkjet head.